Got septorhinoplasty. Got splints and cast removed. Why do I need to have gum in mouth?

i just got septorhinoplasty exactly one week from today and got my splints and cast removed yesterday. when i got my cast removed he also cleaned my nose out but numbed it first.. it left a weird kind of plastic smell in my nose and kind of in my mouth and today its not in my nose anymore but there is a realllllly foul taste in my mouth that i cant get rid of . i have to constantly have gum in my mouth or eating or drinking cause it tastes so bad its like stuck on my tounge any idea of what the reason is ?! i dont know if its connected with my nose or not but i thought maybe it was cause im breathing out my mouth for the most part ..?? Help!!